Remediation of heavy metals in ammunition traps and shooting ranges

ABSTRACT

The invention provides methods of remediating lead and other heavy metals in ammunition traps and shooting ranges. One or more remediation agents is added to a trap or a shooting range. The remediation agent(s) interact with and “fix” heavy metals, rendering them substantially non-leachable. An improved ammunition trap is also provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims priority of U.S. Provisionalapplication No. 60/540,397 filed Jan. 30, 2004, the entire contents ofwhich are incorporated by reference herein.

FIELD OF THE INVENTION

This application relates generally to remediation of heavy metals, andmore particularly to methods for remediating heavy metal ammunition,fragments, fines, and dust found in ammunition traps and on shootingranges.

BACKGROUND OF THE INVENTION

Lead-Antimony alloys and other heavy metals and their alloys areextensively used for ballistics applications such as bullets and shot.Lead alloy usage is in the region of 200-300,000 tonnes per annumworldwide, of which the USA accounts for approximately half. About 70%of ballistic metals are fired on ranges and it is estimated that thereare 9,600 shooting ranges within the USA.

When bullets or shot are fired on ranges they can, under adverseconditions, give rise to significant pollution through the solublizationand corrosion of the lead-antimony alloy in a concentrated area. Asshown in FIG. 1, pure lead in soft water will yield concentrations ofsoluble lead levels of above 0.75 mg/litre at pH 7.5 within days toweeks. Lead-antimony alloys will dissolve at a much faster rate andachieve much higher levels of soluble lead, as a result of redoxreactions occurring between the lead and antimony metals present in thealloy. (FIG. 2.)

Other heavy metals used for ballistics applications that may be presenton shooting ranges include antimony, copper, tungsten, tin, bismuth,silver, nickel, and zinc. All of these metals or their compounds canhave a negative impact on human health or the environment.

To minimize heavy metal pollution, well-managed shooting ranges provideammunition traps (more commonly referred to as “bullet traps”) behindthe target area. Bullets, shot, and other projectiles that are firedpass through the target and impact a bullet stop or “trap,” and theirimpact fragments are contained. Periodically, the traps must berefurbished and the spent bullet fragments removed for recycling.

There are many different designs of bullet traps. A partial listincludes plate and pit, escalator, venetian blind, rubber lamella,granular rubber, and circulating water (snail trap). In general, mostbullet traps fall into two main categories:

Type A: Boxes or similar devices containing materials to absorb themechanical impact of the projectile, e.g., sand, rubber, hydro-gelblocks, rubber or polyurethane curtains, and similar materials.

Type B: Large steel plates to direct projectiles toward a moving liquidenergy dissipation system. Such systems usually utilize flowing water,oil, or similar liquid to minimize abrasion and impact damage within thetrap.

Combinations of the two types are also sometimes employed. Hence, a trapmay contain both an ammunition impact-absorbing and/or deflecting means(e.g., impact plates, deceleration chamber, sand pit, moving fluid,rubber strips or curtains, etc.), and a receptacle for collecting bulletfragments, fines, and/or dust. While minimizing dust, conventionalbullet traps still give rise to fines and other fragments which, onexposure to the environment, can corrode to yield soluble lead saltsthat may be transported to the drainage system of the range by action ofrainwater. Additionally, liquids used in traps of Type B can give riseto heavy metals-contaminated wastes resulting from the corrosion of leaddust and fines in the circulating lubricant systems. What is needed areimproved, environmentally self-remediating ammunition traps, and methodsfor rendering an existing trap self-remediating.

SUMMARY OF THE INVENTION

The present invention addresses the problem posed by heavy metal-basedammunition in ammunition traps and shooting ranges, includingcontamination from spent ammunition, ammunition fragments, fines, anddust. According to a first aspect of the invention, a method ofremediating a heavy metal in an ammunition trap is provided, andcomprises adding to the trap at least one heavy metal remediation agent.As used herein, the term “heavy metal remediation agent” (or moresimply, “remediation agent”) refers to a substance that is capable,either alone or in combination with one or more additional substances,of “fixing” a heavy metal, either by transforming it to a lesswater-soluble form and/or by otherwise rendering the heavy metalsubstantially non-leachable (i.e., by encapsulating the metal in asubstantially non-leachable matrix). Preferably, the remediation agentis capable of reducing the water-solubility of a heavy metal below themaximum amount permitted by statute, e.g., the U.S.-U.T.S. limits. Forlead-based ammunition, a combination of calcium sulfide, calciumcarbonate, and calcium phosphate (or triple super phosphate) ispreferred. In one embodiment, one or more remediation agents is added toan ammunition trap as a block or pellet, a flake, a free-flowing powder,a slurry, or some other suitable form. In the presence of water, theremediation agent interacts with heavy metals from spent ammunition,bullet fragments, fines, and/or dust, and remediates the heavy metal(s)in the trap.

According to a second aspect of the invention, a heavy metal remediationblock or pellet for use in a bullet trap and/or shooting range, and amethod of making same, are provided. In one embodiment, a remediationblock or pellet comprises at least one remediation agent dispersed orotherwise contained in a water-soluble or water-degradable binder ormatrix. Optionally, the block or pellet further comprises one or moresurfactants, dispersing aids, and/or flocculating agents to assistdeposition of precipitated insoluble metal compounds. Such a block canbe formed, for example, by forming a mixture of at least one remediationagent and a water-soluble or water-degradable binder; creating a melt byheating the mixture; and forming a pellet or block from the melt.Remediation block formation can be based, to a degree on the principlesof Integrated Fixation Systems technology detailed by Webster and Hurleyin U.S. Pat. No. 6,838,504, the entire contents of which areincorporated by reference herein.

According to a third aspect of the invention, a method of remediating ashooting range contaminated with at least one heavy metal is provided,and comprises: introducing one or more remediation agents into adrainage system of the shooting range, or, particularly in the case ofan outdoor shooting range, allowing one or more remediation agents tocontact the shooting range (i.e., the ground). Adding a remediationagent or agents to a shooting range's sump, pond, drainage line, etc.,or simply the ground itself, enables the agent(s) to interact with heavymetals from spent ammunition, ammunition fragments, fines, or dust,thereby preventing soluble lead, antimony, and other heavy metals frombeing discharged into public water courses.

According to a fourth aspect of the invention, an improved ammunitiontrap is provided and comprises at least one heavy metal remediationagent in combination with an ammunition trap. In one embodiment, animproved trap comprises at least one ammunition impact-absorbing and/ordeflection means; a receptacle for spent ammunition, fragments, fines,and/or dust; and at least one remediation agent in the receptacle.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages and various features of the invention will become betterunderstood when reference is made to the following detailed descriptionand considered in light of the accompanying drawings, wherein:

FIG. 1. is a graph showing the corrosion of a 2 mm shot of 99.999% leadimmersed in water for 100 days;

FIG. 2. is a graph showing the corrosion of a U.S. No. 8 lead-antimonyshot (nominally sold as containing 2% antimony, but actually assayed at1.25% antimony (w/w); and

FIG. 3 is a schematic illustration of one embodiment of aself-remediating ammunition trap according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

According to one aspect of the invention, a method of remediating one ormore heavy metals in an ammunition trap is provided. In one embodiment,the method comprises adding to the trap at least one remediation agent.Nonlimiting examples of remediation agents include calcium sulfide,calcium phosphate, calcium hydroxide, calcium oxide, calcium carbonate,magnesium sulfide, magnesium phosphate, magnesium hydroxide, magnesiumoxide, magnesium carbonate, apatite, di-calcium hydrogen phosphate,calcium di-hydrogen phosphate, triple super phosphate, dolomite,phosphoric acid, and/or mixed calcium adducts of these agents. Otherexamples of remediation agents include phosphoric acid and its salts,which can be used for lead abatement; the mineral apatite(Ca₅(PO₄)₃(F,Cl,OH), which is functional, but slow; alkaline earthsilicates (e.g., calcium silicate), which operate through sorption andas a consequence of their high alkalinity (hence, their effect is likelynot permanent); hydrated silica and hydrated alumina; and metal-sorbingclays, such as Bentonite and Fuller's Earth. When used by themselves,phosphates are considered suitable for remediation of lead, but they donot remediate other metals.

Environmental remediation agents are available from Solucorp Industries(West Nyack, N.Y.) under the Molecular Bonding System™ or MBS™trademark, and Metals Treatment Technologies (Wheat Ridge, Colo.) underthe Ecobond® trademark. Preferred remediation agents comprise mixturesof technical grade calcium sulfide, calcium phosphate or triple superphosphate, and calcium carbonate, available from Solucorp Industries.“Triple super phosphate” (also referred to as tri-super phosphate, orTSP) is Ca(H₂PO₄)₂.H₂O (CAS No. 65996-95-4). A particularly preferredremediation agent for lead and lead-antimony alloy ammunition is MBS™2.1, a 3:2:1 (wt/wt) mixture of calcium carbonate, calcium sulfide, andtriple super phosphate. MBS™ 2.1 is not pH-dependent, and can remediatelead under conditions ranging from pH 1 to pH 13. In contrast,phosphates and silicates are pH-dependent, with phosphates functionalunder broadly neutral conditions (pH 6 to 8), and silicates functionalunder strongly alkaline conditions (>pH 10). Additionally, the MBS™remediation agent converts soluble lead salts to lead sulfide, which isnon-toxic by oral administration.

The remediation agent(s) is added to the trap as a remediation block orpellet, flakes, a free-flowing powder, a slurry (e.g., an aqueous slurryof one or more remediation agents), or in some other suitable form.Remediation blocks are particularly preferred, as they permit theremediation agent(s) therein to be released in a time-release fashion,with minimal increase in the alkalinity of the system. Applying theremediation agent(s) at too fast a rate, in addition to being wasteful,may lead to a temporary increase in dissolution of fine lead metalfragements in the sludge of the trap, requiring a longer time for thereagent to be fully effective.

The amount of remediation agent(s) added to the trap depends on the typeof trap, the type and amount of heavy metal contamination, theparticular remediation agent(s) employed, and other factors that will beappreciated by a skilled person. Traps that see substantial use in agiven period of time will typically require larger amounts ofremediation agents than traps that see little or infrequent use.

Whether in block, pellet, flake, powder, slurry, or some other form, theremediation agent is added to a region or regions of an ammunition trapmost likely to be exposed to spent ammunition, ammunition fragments,fines, or dust; for example, the pit in a pit-and-plate trap; the sump,water line, or liquid tank in a circulating fluid trap; a receptaclenear a deceleration chamber or impact-absorbing plate; or any part(s) ofthe trap likely to be exposed to heavy metals.

For example, in one embodiment, one or more reagent blocks are placed ina type A ammunition trap (described above) where lead fines may occur.On exposure to moisture, which may cause the onset of the corrosion ofthe lead fragments collected by the trap, the block(s) are activated andliberate their remediation agent, causing continual remediation of thespent lead fragments within the trap during its active use. The block(s)may be replaced during periodic maintenance of the trap. Alternatively,the reagent blocks are incorporated into a rubber-like hydro-gel orother materials from which bullet trap energy-absorbing materials areconstructed.

In another embodiment, one or more reagent blocks are applied directlyto a type-B trap (described above) and will disperse in the liquidsystems to remediate lead fines and corrosion products. Spent lead thatis removed for recycling, though it will be darkly coloured with apassivating corrosion product, and rendered stable to further oxidationand corrosion, will still be recyclable in the same manner as untreatedlead. Addition of the reagent blocks to the liquid lubricants willrender the lubricants free of soluble lead and reduce the risk of aliquid waste hazard, with a consequent reduction of waste disposalcosts.

In a second aspect of the invention, a heavy metal remediation block orpellet, and a method of making such a block or pellet, are provided. Inone embodiment, a heavy metal remediation block or pellet comprises atleast one remediation agent dispersed or otherwise contained in awater-soluble or water-degradable binder or matrix, the compositionbeing of a suitable size and shape (small or medium block, pellet, etc.)to function within one or more areas of the trap. When exposed to water,the binder dissolves or degrades over a period of time, releasing theremediation agent, which interacts with and fixes lead, antimony, andother heavy metals in the trap.

Nonlimiting examples of binders include water-soluble and/orwater-degradable waxes, such as hydratable and/or degradablepolyethylene glycols and copolymers of ethylene glycol; polyacrylatesand/or hydratable celluloses compounds, and their methyl, ethyl, propyland/or butyl ethers. Mixtures of binders may also be used.

Optionally, the reagent block or pellet further comprises one or moresurfactants, dispersing aids, and/or flocculating agents. Nonlimitingexamples of useful surfactants and dispersants includepolyethoxyethylene ethers of fatty acids, polyethoxyethylene esters offatty acids, and polyethoxy ethers of alcohols (e.g., polyether alcoholshaving the formula CH₃(CH₂)_(x)—O—(CH₂CH₂)_(y)—OH, where x > or =5 andy>1). Typical surfactant concentrations within a reagent block are 0.1to 1% by weight of the total block. Nonlimiting examples of flocculantsinclude Superfloc A120, A130, and A150, from Cytec Industries B.V.).

A heavy metal remediation block or pellet can be formed in astraightforward manner. In one embodiment, the method comprises forminga mixture of at least one remediation agent and a water-soluble orwater-degradable binder (and, optionally, one or more surfactants,dispersing aids, and/or flocculating agents); creating a melt by heatingthe mixture; and forming a pellet or block from the melt. For example, ablock or pellet can be “cast” by pouring the melt into a mold andallowing it to harden. Pellets or blocks so formed can added to anammunition trap to remediate heavy metal ammunition fragments, fines,and dust.

To increase production speeds, the remediation blocks and pellets may beformed by a number of mass manufacturing processes, e.g. prilling orcompressing into blocks or tablets; flaking; etc., and the invention isnot limited by the physical methods of preparation of the blocksdescribed herein.

In another aspect of the invention, heavy metals from spent ammunition,ammunition fragments, dust, fines, etc. on a shooting range areremediated by introducing one or more remediation agents into thedrainage system of an indoor or outdoor shooting range (e.g., a sump,pond, and/or drainage line), or simply the ground itself in an outdoorrange. The remediation agent(s) interact with heavy metals from spentammunition, ammunition fragments, fines, dust, etc., thereby preventingsoluble lead, antimony, and other heavy metals from being dischargedinto public water courses.

According to a fourth aspect of the invention, an improved ammunitiontrap is provided and comprises at least one heavy metal remediationagent in combination with an ammunition trap. In effect, the trap is“environmentally self-remediating,” as it remediates lead and otherheavy metals from ammunition that enters the trap. In one embodiment, animproved trap comprises at least one ammunition impact-absorbing and/ordeflection means; a receptacle for spent ammunition, fragments, fines,and/or dust; and at least one remediation agent in the receptacle. Inalternate embodiments, the trap has an alternate configuration and/orthe remediation agent(s) is disposed elsewhere within the trap.

Referring to FIG. 3, an improved ammunition trap in accordance with oneembodiment of the invention is shown. The trap 10 is of the circulatingwater type (sometimes referred to as a “Snail Trap”), and includes adeceleration chamber 12 through which water circulates. A bullet orbullet fragment 14 enters the trap and travels along a path 14 a untilit contacts the deceleration chamber and stream of circulating water.The bullets travels around the chamber until it loses its kinetic energyand falls through a gap 16 in the chamber and is caught by a screen orgrill 18. Smaller bullet fragments, fines, and dust, as well as water,pass through the screen 18, and are retained in a receptacle 20. Thereceptacle also acts as a reservoir for water used in the system. Overtime, sludge accumulates at the bottom of the reservoir. Water from thereceptacle is pumped through a return line 24 back to the decelerationchamber 12.

According to the invention, one or more remediation agents 30 isintroduced to the trap, either as a block, pellet, powder, slurry, orother form, by adding the same to the water reservoir/receptacle 20, aninput line (not shown), or some other suitable location. If a block orpellet of the type above is used, it has the advantage of releasingremediation agent(s) into the system at a measured rate; that is, in atime-released fashion.

The following are nonlimiting examples of the invention:

EXAMPLE 1

A heavy metal remediation block consisting of technical grade calciumsulphide, calcium phosphate, calcium carbonate, polyethylene glycol wax(approx. mol. weight 1,500) in a wt.-to-wt. ratio of 2:1:3:2) isprepared by blending the ingredients together, heating the blend to 100°C. (thereby causing the wax to melt), and casting the melt into 5 gramto 100 gram blocks. A reagent block approx 0.5 inch square will dispersein water in 24-48 hours.

EXAMPLE 2

A heavy metal remediation block consisting of technical grade calciumsulphide, calcium phosphate, calcium carbonate, calcium hydroxide,polyethylene glycol wax (approx. mol. weight 1,500) in a wt. to-wt.ratio of 2:1:1:2:2 is prepared by blending the ingredients together,heating the blend to 100° C. (thereby causing the wax to melt), andcasting the melt into 5 gram to 100 gram blocks. A reagent block approx0.5 inch square will disperse in water in 7-14 days.

A 5 g block prepared as described herein, when dispersed in water, willadsorb in excess of 1.8 grams of soluble lead. If an excess of reagentis used (relative to the amount of soluble lead present) leachate levelsare reduced below UTS limits by US-TCLP testing procedures.

Immersion of a 5 g block prepared according to example 2 in water for aperiod of 21 days resulted in no discernible decrease in chemicalefficacy. Immersion of the same size blocks in running fresh water for21 days, followed by exposure to soluble lead, resulted in only a 10%loss of efficacy. Dissolution and or longevity of the efficacy of thetreatment block may be controlled by block size and shape.

EXAMPLE 3

A heavy metal remediation trial was conducted on four circulating-waterbullet traps (also known as “Snail Traps”), supplied by Savage RangeSystems (Springfield, Mass.) in an indoor shooting range. Severalthousand rounds of ammunition are fired on the range annually. Four,8-foot wide bullet traps were situated in a row immediately behind a30-foot wide target area. The sumps of the traps were interconnected tomake one combined sump operation below the deceleration chambers of thefour traps. Bullets passing through the targets pass into the traps andare carried on the traps' circulating-water systems until they loosetheir ballistic energy and are deposited on a bullet capture screenbelow each trap. Owing to the construction of lead-antimony alloy andother frangible bullets, a small proportion of each spent slug may becarried by the circulating-water system and subsequently settle as asludge (in this case equating to approximately 72 cubic feet) in thewater sump or reservoirs situated immediately beneath the traps.Combined, the four traps contained approximately 280.5 gallons of watercontaining 1% of a conventional alcohol glycol-based antifreeze. Priorto treatment, the water circulating in the traps (being a composite ofthe sludge and water) exhibited 173 mg/liter of soluble lead. The sludgeexhibited 1,340 mg/liter of soluble lead (by TCLP SW846 procedure)

20 lbs of a remediation agent (MBS 2.1, from Solucorp Industries) wasadded to each of the four traps, equating to a treatment dosage of3.44%, and the traps maintained in active range use for a further sixweeks. Post-treatment and curing, the soluble lead in the watercirculating in the traps had fallen to 7.68 mg/liter, and the sludgeexhibited 2.87 mg/liter of soluble lead (by TCLP SW846 procedure).

The invention has been described with reference to various embodiments,figures, and examples, but is not limited thereto. Persons havingordinary skill in the art will appreciate that the invention can bemodified without departing from the invention, which is limited only bythe appended claims.

1. A method of remediating a heavy metal in an ammunition trap,comprising: adding to the trap at least one heavy metal remediationagent.
 2. A method as recited in claim 1, wherein the at least oneremediation agent is selected from the group consisting of calciumsulfide, calcium phosphate, calcium hydroxide, calcium oxide, calciumcarbonate, magnesium sulfide, magnesium phosphate, magnesium hydroxide,magnesium oxide, magnesium carbonate, apatite, di-calcium hydrogenphosphate, calcium di-hydrogen phosphate, triple super phosphate,dolomite, phosphoric acid, mixed calcium adducts thereof, phosphoricacid and its salts, alkaline earth silicates, hydrated silica, hydratedalumina, metal-sorbing clays, and mixtures thereof.
 3. A method asrecited in claim 1, wherein the at least one remediation agent comprisesa mixture of calcium sulfide, calcium carbonate, and calcium phosphateor triple super phosphate.
 4. A method as recited in claim 1, whereinthe at least one remediation agent comprises a 3:2:1 (wt/wt) mixture ofcalcium carbonate, calcium sulfide, and triple super phosphate.
 5. Amethod as recited in claim 1, wherein the at least one remediation agentagents is added to the trap as a block or pellet, a flake, afree-flowing powder, or a slurry.
 6. A method of remediating a heavymetal in an ammunition trap, comprising: adding to the trap a blockcomprising at least one remediation agent dispersed in a binder.
 7. Amethod as recited in claim 6, wherein the at least one remediation agentis selected from the group consisting of calcium sulfide, calciumphosphate, calcium hydroxide, calcium oxide, calcium carbonate,magnesium sulfide, magnesium phosphate, magnesium hydroxide, magnesiumoxide, magnesium carbonate, apatite, di-calcium hydrogen phosphate,calcium di-hydrogen phosphate, triple super phosphate, dolomite,phosphoric acid, mixed calcium adducts thereof, phosphoric acid and itssalts, alkaline earth silicates, hydrated silica, hydrated alumina,metal-sorbing clays, and mixtures thereof.
 8. A method as recited inclaim 6, wherein the at least one remediation agent comprises a mixtureof calcium sulfide, calcium carbonate, and calcium phosphate or triplesuper phosphate.
 9. method as recited in claim 6, wherein the bindercomprises a water-soluble and/or water-degradable wax.
 10. A method asrecited in claim 9, wherein the water-soluble and/or water-degradablewax is selected from the group consisting of hydratable and/ordegradable polyethylene glycols, copolymers of ethylene glycol, andmixtures thereof.
 11. A method as recited in claim 6, wherein the binderis selected from the group consisting of polyacrylates, hydratablecellulose compounds, methyl, ethyl, propyl and/or butyl ethers ofhydratable cellulose compounds, and mixtures thereof.
 12. A method asrecited in claim 6, wherein the block further comprises one or moresurfactants, dispersing aids, and/or flocculating agents.
 13. A methodas recited in claim 12, wherein the block contains at least one compoundselected from the group consisting of polyethoxyethylene ethers of fattyacids, polyethoxyethylene esters of fatty acids, and polyethoxy ethersof alcohols (e.g., polyether alcohols having the formulaCH₃(CH₂)_(x)—O—(CH₂CH₂)_(y)—OH, where x > or =5 and y>1.
 14. A methodfor making a heavy metal remediation block or pellet, comprising: atleast one heavy metal remediation agent and dispersed forming a mixtureof at least one remediation agent and a water-soluble or water solublebinder; heating the mixture to form a melt; and casting the melt into apellet or block.
 15. A method as recited in claim 14, wherein themixture further comprises one or more surfactants, dispersing aids,and/or flocculating agents.
 16. A heavy metal remediation block orpellet, comprising: at least one heavy metal remediation agent and oneor more surfactants, dispersing aids, and/or flocculating agents,dispersed in a water-soluble or water degradable binder.
 17. A method ofremediating a shooting range contaminated with at least one heavy metal,comprising: introducing one or more remediation agents into a drainagesystem of the shooting range.
 18. A method of remediating an outdoorshooting range contaminated with at least one heavy metal, comprising:allowing one or more remediation agents to contact the shooting range.19. An improved ammunition trap, comprising: at least one heavy metalremediation agent in combination with an ammunition trap.
 20. Animproved ammunition trap, comprising at least one ammunitionimpact-absorbing and/or deflection means; a receptacle for spentammunition, fragments, fines, and/or dust; and at least one remediationagent in the receptacle.
 21. In a bullet trap having a box and animpact-absorbing material, the improvement comprising a heavy metalremediation agent inside the box.